Process of purifying and concentrating sulphur dioxide



Nov. 9 1926. I 1,606,299

I G. C. HOWARD PROCESS OF PURIFYING AND GONCENTRATING SULPHUR DIOXIDE Filed April 3 1923 2 INVENTOR;

Geg 61%2/4/14 ATTORNEY,

sentiall by ime! 1 7 an solution 1:9" eu bs'tan t lly t0 expe'l' -t e 'diss'efiiec s'til ph ing andxIry the gas and finall 'l iqu'e' and re frig'efzit 25 v Themot c6 primariIyby the-c in the ori'gflfial gas handicapped-fin" s k H of using w 1'te 5es *theitb'sliifptiony-niudihxh B0 The quanti'ty'efQW-t. required ES 151'}; consequently the p Ives gaff r la sum ition t 'e siilphur f V preseui'e or Tower these 'cjeh'c hydr emand eppext t y. re

' by beefing z f lhe jab ici bn fer" this is thetilpheholii t vfith sulphur dioxld eith its 'bbilifig pomt -h verse when heated in the absence 9ft? ti: 7 W point of water atnd that its vapor tension which will reverse when heated 1n the presbe practically nil gt the temperature at which ence of sufiicient steam. The'hydrocarbon's on; I

the other hand which contain no hydroxyl groups react with sulphur dioxide either dry or evelr'in the. presence of water to form sulphinic acid combinations which reverse from other sources.

I would specifically omit from consideration as an absorption medium in this process 1 any alcohols of thesaturated hydrocarbon series such as methyl and the corresponding higher alcohols, as not complying with economic requirements for one reason or another. Also I would deny all claim to vege; table oils as not being compounds which show materially if any higher absorption for sulphur dioxide than water does, hence not meeting one of the objections of this invention. Finally I would not exclude anthracene and other of the higher solid hydrocarbons since their coeificient of absorption is 'sufliciently high to meet requirements and would limit the quantity of such constituents only by the amount which will remain in solution in the absorption medium at the temperatures obtaining throughout the cycle of o eration a11d by economic reasons as regar s cost.

My improved process may be described as follows, reference being had to the accompanymg drawing which illustrates in somewhat diagrammatic form and shown on two elevations the'apparatus employed in carry- .mally a part of such burner.

ing out said process.

The reference numerical 1 designates a sulphur burner which typifies the source from which a sulphur dioxide mixture is obtained, and 2 is a combustion chamber, nor- 3 indicates a cooler whereby the gas mixture is cooled by air or water outside of the pipes. A cooling and scrubbing tower 5 is provided wherein the gas mixture is dried and cooled to/the'predetermined temperature for absorption and in which any flue dust, fume an other impurities can be removed. This is accomplished by circulating strong sulphuric acid'through the'tower 5 countercurrent-to the gaseous mixture. The circu;

lat-ion of acid in the tower 5 is accomplished by pump 6 through pipe 7 in which cycle is an acld storage tank and cooling coil, not shown, to remove the heat absorbed from the gas. mixture.

The gas entering said tower '5 at 8 is disdescribed which enters the absorption towerg;

10 at 12, and exits into pipe 13 saturated with sulphur dioxide. The waste gas from tower lOpassesthrough pipe 11 to a Nash pump 15 or equivalent, which serves to furnis'h draft on all the preceding equipment .and to function as a final absorption appliance for the spent gases, wherein said gases are brought into contact with the absorption liquor conveyed to said pump by pipe 16 as will be hereinafter explained. From the pump 15' the residual-gases free from sulphur dioxide go to waste through pipe 17.

13' is a pipe carrying the liquor saturated with sulphur dioxide from tower 10 to a storage tank 18. A pump- 19 delivers this liquor thru pipe 20 to a double pipe heat lnterchanger 21 wherein it is heated preparatory to entering the bottom .of boiling tank 22. Said tank 22 may be described as a modified vertical fire tube boiler in which the liquor pas'sesupward inside the tubes 23 and is heated by steam outside the tubes. In tank 22 the gas-saturated liquid is heated to a point above the boiling point of water but preferably below its own boiling point whereby the escape and removal of the absorbed gases is readily eifected, with- "out accompanying vapors from the absorp tion liquor in undue quantities. Rising in the tank 22 the liquor overflows at 24: into a finishing tank 25 from which it exits at 26. The finishing tank 25 may likewise be Illustrated as a vertical boiler but differs from tank22 in that provision is made to distribute the liquor to the rim of the tubes 27 so that itv flows down as a thin stream on the surface, of ach tube. In other words the tubes are not kept full of the liqlior as inthe tank 22 for the desired action inthis tank is best secured with the liquor spread out over as large an area as practicable,,and thereby causing an economically complete removal of the sulphur dioxide from the absorption liquor in the form of gas. Steam outside the tubes 27 maintains the temperature and if desired raises it.

In tanks 22 and 25 the dissolved sulphur dioxide gas is expelled and exits thru pipe,

28. The hot spent liquor returns thru pipe 29 to the interchanger 21 wherein it serves to heat the incoming saturated liquor and then passes thru pipe 30 to a storage tank 31. Pump 32 deliversthis spent liquor to cooling coils 33 wherein it is cooled by suitable means to the predetermined temperature for absorption and passesin part'by pipe' 12 to the tower and in part by pipe 16 to the pump and thence thru-pump 34 to the absorption tower 10 wherein it is resaturated with sulphur dioxide and repeats the described cycle.

The sulphur dioxide expelled from the" tanks 22 and 25 is dry and pure save that, it will cont in a small amount of the vapor of the absorption liquor and a normal small component of gases other than sulphur dioxide. This sulphur dioxide passes thru pipes 28 to double pipe coils or equivalent apparatus in which it is cooled and thence to a Nash pump 36 or equivalent. 'The' 'function of pump 36 isto furnish suction, or

vacuum if desired, in the boiling and finish-- ing'tanks and to remove the condensed vapor of the absorption liquor carried by the sulhur dioxide. The displacement liquor used in the Nash ump 36 will normally be the same as the, a sorption liquid used, in tower 10 and will circulate thru a cycle not shown including a cooling'coi l. From pump 36 the gas passes to a compressor 37 .thru a receiver 38 thence to refrigerating coils 39 and to a storage. tank 40. Any gas not liquefied by said compressor 37 and the succeeding refrigeration may be returned to the original gas-mixture for passage again thru the ab-v sorption towers.

It will thus be seen that my process consists essentially in drying and cooling a gas mixture containing sulphur dioxide, absorbing the sulphur dioxide in said dried and cooled mixture in a non-aqueous liquid which has a boiling point higher than water, heating said saturated liquor 'to expel the-absorbed gas to a temperature above the boiling point of water, but below its ownboiling point, causing said 'hot liquor to spread out to give maximum surface exposure where- -scrubbing the gases and vapors expelled by the removal of the gas is aided, returning said hot spent liquor thru a heat interchanger wherein its heat is transferred to the incoming saturated liquor, thence further cooling said spent liquor by suitable means and againexposing it to the gas mixture for resaturat-ion with sulphur dioxide, cooling and from the above heated liquor, compressing and refrigerating said resulting gases whereby the sulphur dioxide is liquefied and returning the non-liquefied constituents to the original gas mixture for passage again thru the absorption liquor.

Having described my claim is:

'1. The process of recovering sulphur diinvention, what I exposing sa'idgas mixture to a non-aqueous:

liquid cyclic hydrocarbon .free from mono and polyhydric phenols whereby sulphinic acid compounds are formed that decompose with the liberation of sulphur dioxide on heating-in the absence of water, removing said resulting liquid hydrocarbon from contact with the gas mixture and subjecting it to heat in the absence of water, recoverin the sulphur dioxide thereby liberated an again exposing said liqudhydrocarbon after cooling to a similar aforesaid gas mixture.

3. The process of recovering sulphur dioxide from a dry gas mixture consisting in.

exposing said gas mixture to a non-aqueous liquid hydrocarbon derived from coal tar and free from mono and polyhydric phenols whereby compounds are formed that decompose with the liberation of sulphur dioxide on heating in the absence of water, removing said resulting liquid hydrocarbon from contact with the gas mixture and subjecting it to heat in the absenceof water, recovering the sulphur dioxide therebyliberated and again exposing said liquid hydrocarbon after cooling to a similar aforesaid gas mixture.

4. The process of recovering sulphurdioxide from a dry gas mixture consisting in a 1 exposing said gas mixture toa non-aqueous liquid hydrocarbon derived from coal tar and free from 'mono' and olyhydric phenols whereby sulphinic aci com ounds are formed that decompose with the li era'tioqof sulphur dioxide on heating in the absence of water, removing said resulting liquid hydrocarbon from contact with the gas mixture and subjecting'it to heat in the absence of water, recovering the sulphur dioxide thereby liberated and again exposing said liquid hydrocarbon after cooling to a similar aforesaid gas mixture.

GUY o. HO A D; 

